Castle and Keep
by Alchemine
Summary: When a quiet evening takes a frightening turn, Mildred and Miss Hardbroom are forced to cooperate to find out what happened and try to repair it. (CITV 1998 version)
1. Chapter 1

Like all old castles, Cackle's Academy had its share of legends. There were a hundred chilling tales of wailing ghosts and gory murders that put Sir Walter and his Wet Week to shame, and that everyone felt duty-bound to repeat to the gullible first-years, just as they had been told themselves when they were new girls.

Schools being what they were, Cackle's was also host to a multitude of juicy rumours about its staff, and about one member of it in particular. If you had been a pupil there at any time in the last twenty years, you had heard, variously:

– That Miss Hardbroom only slept two hours a night, and they were always two different hours, so you could never be quite sure when it was safe to slip out of your room.

– That Miss Hardbroom had not slept since 1987, and then it had only been a ten-minute nap.

– That Miss Hardbroom never slept at all.

– That Miss Hardbroom was a vampire who was specially adapted not to sleep during the school term, but spent all the holidays unconscious in a coffin below the sub-dungeon, from which she rose fully dressed and coiffed just before the first returning pupil's broomstick made its way into the courtyard. (Some versions of this story held that if you failed your first-year exams, Miss Hardbroom would be allowed to drain all your blood to gain strength for her long summer hibernation, and the school would put it about that you had been sent home in disgrace.)

The truth, of course, was that Constance Hardbroom was as human as her gossipy young charges, and she did sleep "most nights," as she would have put it. Every now and then, after an especially trying day, she went so far as to retire before midnight, and this was one of those times. At half past eleven, she was tucked up in bed—not the stone slab or wooden casket that generations of Cackle's pupils had imagined, but a proper double bed with a blanket and pillow—and reading a book that Miss Drill had forced upon her some weeks ago. The descriptions of magic in it were quite inaccurate, and anyone with a brain could tell that the twitchy professor in the purple turban was up to no good, but she was halfway through and thought she ought at least to see how it ended. Perhaps then Miss Drill would stop pestering her about whether she had liked it or not.

As she was perusing the rules of Quidditch and thinking that it sounded a more interesting sport than any of the ones the girls at Cackle's were forced to do, she heard the patter of teenage footsteps in the corridor and huffed out a sigh. Of course they would have to get up to mischief on one of the rare nights when all she wanted was to read for a bit and go to sleep. She laid the book open and face-down on her chest, keeping her place, and waited to see which direction the steps would go in. If the perpetrators were already on their way back from whatever unauthorised midnight expedition they had been on, she might ignore it, just this once.

To her surprise, the steps went neither upstairs nor down. Instead, they shuffled to a halt outside her door and hesitated there, as if whoever owned them were uncertain of what to do next. With simmering irritation that was beginning to approach a rolling boil, Constance got out of bed, went to the door and jerked it open to reveal the familiar and infuriating shape of Mildred Hubble, one hand lifted as if she had been about to knock.

"Mildred Hubble, what are you doing out of bed at this hour? More importantly, what are you doing outside my door? Shouldn't you and your little gang be downstairs raiding the kitchen or creeping about the …" Constance trailed off as she registered Mildred's expression—not one of guilt at being caught out, but of desperate worry, verging on terror.

"Is there something I ought to know, Mildred? And if there is, tell me quickly, because I was in bed and I would like to return there as soon as possible."

"Listen, Miss Hardbroom. Do you hear it?"

"Hear what? Really, Mildred, this is not the time for riddles—"

"Just listen," Mildred said. Her voice was so tense and anxious that Constance bit back the rest of her reprimand and did as the girl had commanded.

"You do hear it, don't you?" Mildred's eyes were wide, her face pale between the dark curtains of hair that fell to either side. "Please say you do."

Constance nodded slowly. She wasn't quite certain what she was hearing, but she did hear something—a soft and but insistent chorus of whispers that rose and fell and occasionally burst out in a quick sharp exclamation. It was like standing in the Great Hall when the whole school was gathered for assembly, hearing the babble of a hundred voices all together, but not being able to pick out what any individual voice was saying. The sound seemed to come from everywhere, just low enough to escape notice if you weren't listening for it, but impossible to ignore once you were.

"I hear it," she said, and Mildred let out a breath she had clearly been holding. "What is it? How long has it been going on?"

"I'm not sure, Miss Hardbroom. I was still awake—with my candle out, of course," she added, although enforcing the lights-out rule was not top of mind for Constance at the moment. "I was just lying there in the dark, thinking, and then I began to hear it little by little, until it was like this. I thought it was my imagination at first."

"You are prone to flights of fancy, Mildred," Constance said dryly, "but it seems not this time."

"No, Miss. We have to do something, we..."

" _We_ are not going to do anything, Mildred. _You_ will go back to your room at once and stay there, and I will go and fetch Miss Cackle, and she and I will get to the bottom of it."

Mildred shook her head. "You can't, Miss."

"Don't presume to tell me what I can and can't do, girl. Now go back to your –"

"You _can't_ ," Mildred insisted. She drew herself up, frightened but defiant, and Constance realised that standing face to face in bare feet and slippers, she and Mildred were very nearly the same height. When had the girl grown so much, and how had she not noticed until now?

She planted her hands on her hips to create a more imposing silhouette.

"Why not?" she asked. "And before you answer, let me remind you that it had better be a very, _very_ good reason."

"Because she's not here," Mildred said. "I already checked, and she's gone. And so are Miss Crotchet and Miss Drill. And –" Her voice quivered. "And so are all my friends. Maud and Enid and Ruby and everyone. They're all gone, Miss Hardbroom. There's no one in the school but you and me."


	2. Chapter 2

There had been a time when Constance would have disbelieved Mildred's story on principle, and they would have spent the next quarter-hour touring the castle, checking every room, until she was forced to admit that Mildred hadn't been lying. After four years of dealing with one Mildred-related drama after another, she simply accepted it to save the effort. It would turn out to be true in the end anyway.

"Perhaps you should come in," she said.

Mildred recoiled as if Constance were the spider from the poem and she were the fly. "Into your room, Miss?"

"Yes, yes," Constance said impatiently. "Come along, don't dawdle."

Mildred stepped over the threshold with the expression of someone going to her own execution, and Constance shut the heavy iron-studded oak door behind her and locked it tight with a casual zap of magic. Inside, the whispering voices were muted, but she could hear them still, nagging away at the very edge of her awareness and putting her nerves on edge. She turned from the door to find Mildred gazing about the room in wonder, her eyes flickering from sofa to rug to dressing table to bed as if she had never seen such objects before in her life.

"What on earth are you gawping at, Mildred?"

"Nothing, Miss Hardbroom," Mildred said hastily. "It's only—you have such nice things."

"Well, what did you expect, a rack and an iron maiden? Never mind, don't answer," she said as Mildred opened her mouth, most likely to put her foot right in it. "Sit down and tell me everything you know. You can begin with when you last saw anyone other than me."

"Before lights-out." Mildred perched on the very edge of the sofa as if she thought she might need to leap up and flee at any moment. "Maud came into my room to talk for a few minutes when we'd finished getting ready for bed, and then we said goodnight and she left. I think I heard a few other people walking past after that, but I can't be certain. I wasn't really paying attention."

A sharp remark about how Mildred rarely _was_ paying attention rose to Constance's lips, but she held it back and sat down in a chair facing the girl. "Very well. And at what time did you leave your room again, and where did you go?"

"About eleven, I think. I went to Maud's room to ask if she could hear the sound, and when she wasn't there I thought she might have gone to Enid or Ruby or Jadu, so I checked their rooms and they were empty, and so were all the other rooms on my floor. I was scared there had been some sort of emergency and no one had told me, so I tried to find Miss Drill and then Miss Crotchet and then Miss Cackle, and when they were all missing too, I came here."

"For goodness' sake, Mildred, did you not think I might need to know about it sooner? Why did you go to the rest of the staff before me?"

"I didn't want to bother you unless it was really important." Mildred hesitated. "You do get a bit cross about things, you know."

Constance had a sudden strong memory of sitting at a table in the dungeon two years ago, with the ink still drying on her letter of resignation, insisting to Mildred that she did not _shout_. It seemed they had made little progress since that day. Why did this girl, of all the hundreds she had taught, always throw her so off balance and make her think about things she would rather not? Why couldn't she be in this situation with Ethel Hallow, who was as ordinary and predictable (and, even Constance had to admit, rather dull), as she was talented at charms and spells?

"Never mind, it can't be helped now," she said, recovering. "So you spoke to Maud at nine and went looking for her again at eleven. I made my evening rounds at half past nine and saw no one in the corridors, but I did stop at Miss Cackle's room just after ten to speak to her. She asked me to stay and have a cup of hot chocolate, but I said no because I wanted an early night. By half past ten I was in my own room reading, and I neither saw nor heard anyone after that."

Mildred looked wistful at the mention of hot chocolate, which the girls were not allowed except on very special occasions, but she made an effort to follow along and put it all together. "So...whatever happened, it was sometime between half past ten, when you went to bed, and eleven, when I got up?"

"It would seem so," Constance said.

"But what could it have been?"

"I've no idea, Mildred. We shall have to see what we can find out. What is the correct magic to use when you need to find something that is lost?"

"A Restoring Spell," said Mildred promptly, and Constance nodded in approval. "But that's for things, not people, and only one at a time. Maybe scrying?"

"We can try," Constance said.

They tried both separately and together, but the glass, when asked where the missing teachers and pupils were, first darkened and then showed only a flat, featureless grey, without even the subtle variations of clouds or fog. Frustrated, Constance terminated the spell and set the mirror down with an angry thump, facing the wall.

"I'm sorry it didn't work," Mildred said tentatively as she watched Constance pace the room.

"You had the right idea for once, Mildred. It ought to have worked. I don't know why it didn't." She stopped abruptly on her third pass in front of the girl. "I don't suppose you've gone outside at all since you noticed people were missing?"

Mildred shook her head. "No, I was afraid whatever was making that whispering sound would be out there. It seemed safer in the castle, even with everyone gone."

"I wonder...Help me with these shutters." Constance was already at the casement and undoing the latch as she said it, and Mildred came too and dragged the left-hand shutter open—they were heavy, and tended to catch on the stone sill—while Constance took the right. With a tortured _screeee_ sound from the hinges, the shutters parted, and both Constance and Mildred drew in a sharp breath of shock so perfectly synchronised they might have rehearsed it.

The evening had been cool and rainy, but instead of looking down into the wet courtyard, they found themselves staring at the same solid grey nothing they had seen in the mirror. It began at the edge of the outer sill and seemed to go on, flat and uniform, into infinity. Mildred put out an exploratory finger to touch it, and Constance seized her wrist to stop her.

"Not with your hand, Mildred! Go and fetch a pencil from my desk."

Mildred ran to do it and came back in a few seconds with a red pencil, which Constance took by one end and gingerly extended through the window. When it reached the beginning of the grey area, it met with a springy sort of resistance, as if she were prodding at an inflated balloon. She pushed a little harder, and all at once there was a pop—something more felt than heard—and the pencil was sucked away from her grip and vanished. For a split second, the whispering voices surged, swelling until she could almost make out what they were saying, and then faded again.

"Oh, _crumbs_ ," said Mildred.

"Exactly," said Constance.


	3. Chapter 3

They repeated the experiment with a nail file, a bit of rolled-up paper, and Miss Drill's book, but no matter what object they used, the result was the same: it was whisked out into the grey void and vanished without a trace. On the last attempt, they both heard what sounded like a shriek amid the chorus of voices, and after exchanging a single horrified glance, slammed the shutters again. Mildred did up the latch and then leant against the wall on her side of the window, nursing a pinched finger and breathing hard.

"This is bad, isn't it?"

"Inelegantly phrased, but accurate," Constance said. She was feeling a bit breathless herself, but she was not about to let Mildred see that. She steepled her fingers under her chin while she thought a moment, and then said, "All right, the first thing to do is to find out whether we're completely surrounded by...whatever it is. You shall stay here while I go and look. Oh, good heavens, girl, don't shake your head at me that way. This room is the safest place in the castle—I've seen to that—and you'll be quite all right until I come back."

"It isn't that," Mildred said. "I'm not frightened of staying here on my own. I want to help. I won't do any magic if you don't want me to, but at least I can keep a lookout. You haven't been out there yet, Miss Hardbroom, but I have, and it's awful walking around in the dark with those voices whispering at you. Anything might happen."

Constance studied Mildred's face and saw nothing but earnestness and good intentions on it. From long, painful experience, she knew that Mildred's good intentions had a way of going awry, but against her better judgment, she yielded.

"Very well, Mildred." She picked up a lantern from her desk and lit the fat white candle inside with a spark from her fingertip, then lit one for Mildred as well. "Come along, and for goodness' sake don't touch anything or make a noise."

"No, Miss Hardbroom."

Lanterns in hand, they crossed the room and re-entered the tenebrous gloom of the corridor. The voices greeted them with even more urgency than before, and this time Constance thought she could understand snatches of their speech here and there.

... _this_

 _open_...

 _...stop...stop_...

 _...help me_

 _why..._

She glanced over at Mildred, who looked tense and watchful in the flickering candlelight, but Mildred still seemed to hear nothing but incomprehensible sounds. Clasped round the ring handle of her lantern, Mildred's hand sported ink smudges and bitten nails with traces of chipped green varnish, but it was steady and resolute as she held the light aloft, and Constance suddenly found herself glad to have the girl's company after all. It was not an emotion she had ever expected to experience, but there it was.

"Which way are we going?" Mildred asked.

"Up to the west tower," Constance said. "From the parapet we can see all round the castle at once, if we can get onto the walkway, that is. We shall have to be very careful going through the door. I don't know what happened to the things that were pulled through that barrier outside my window, and I don't care to find out."

"Neither do I," Mildred said with a shudder. "I'll follow you. The secret stairs are fastest."

The secret stairs were not really secret—when Constance had been a pupil at Cackle's, everyone had known about them by the end of their first term, and nothing had changed since then—but somehow the name persisted. In the castle's original incarnation, they had been a way to escape during sieges and uprisings, either by broomstick flight from the tower top, or by a network of underground tunnels that could be entered through the dungeon. Now they were mainly a shortcut that the girls used to get to lessons when they were late, and to visit their friends on other floors when they should have been sound asleep in bed.

Constance gave the concealed stone that opened the stairs a sharp jab, and a door swung silently toward them on hinges that each new generation of girls kept well oiled. As it did, she had a sudden, terrible moment of certainty that it would open on more of that grey blankness, and that she and Mildred would be trapped not only in the castle, but in this small section of it, forever. But all the door revealed was the dark passageway with its narrow, uneven steps winding upward, a hollow worn into the centre of each one by centuries' worth of treading boots. Damp, frigid air wafted out, and Constance shivered; ever since the night two years before when she had gone into a snowstorm to look for a monster, cold had made her feel uneasy.

"Are you all right, Miss Hardbroom?" Mildred touched Constance's arm lightly, and she shook off her nerves and took a firmer grip on her lantern.

"Don't be silly, Mildred, of course I'm all right. What are you waiting for?" She set a slippered foot on the first stair and began to climb with Mildred just behind her. In the close confines of the stairwell, the whispers should have been dulled, but they seemed as loud as ever in her ears.

 _can you..._

 _...come..._

 _...stop STOP..._

 _...find that..._

 _here..._

 _...no!_

Grimly, she climbed on, up and around the spirals one after the other. There were three hundred and twenty-three steps altogether, and long before they reached the trapdoor that opened onto the tower walkway, the muscles in her thighs and calves were on fire and begging for mercy. Even Mildred, who was put through worse paces several times a week during Miss Drill's P.E. lessons, looked as if her normally boundless energy were running out.

"I've never climbed all the way to the top in one go," Mildred said faintly. "It's farther than I thought. Can't you vanish us instead?"

"I don't dare 'vanish' anyone, Mildred, until I know it's safe in the place where I intend to reappear." Constance tried to keep her voice steady, but didn't succeed as well as she had hoped. "Keep climbing, girl. I'm nearly three times your age, and if I can do this, so can you."

They climbed on a few more steps, and Mildred said "Can I ask you something, Miss Hardbroom?"

" _May_ I ask you, Mildred. Go ahead."

"Where did you learn how to vanish like that? I've never seen Miss Cackle or Miss Bat or Miss Crotchet do it."

"I learnt it from my tutor at witch training college," Constance said, thinking with an internal shudder of those endless lessons. It had been worth it in the end, but the process had been dreadful.

"Oh, _her_ ," said Mildred, and even though Constance could not see her face, she knew Mildred was scowling, a sentiment she heartily agreed with when it came to Mistress Broomhead. "Isn't there anyone else who can teach it? I remember you said a long time ago that we could learn one day."

Constance considered that as she forced her trembling legs up another step. Would it not be a coup if she could teach such a rarefied form of magic to Mildred Hubble, of all people? Even more, would it not go at least partway toward repairing what had been done to her if she could teach it without Mistress Broomhead's cruel methods?

"Mildred, if you pass all your subjects and exams this year, then I shall teach you myself when you're ready. Whether you are still a pupil here or somewhere else, you may come to me and I will see to it that you learn."

"Really? Do you promise?"

"Yes," Constance said. "And you know I always keep my promises."

"I know," Mildred said, and now there was a smile in her voice. "Thank you, Miss Hardbroom."

"You're welcome, Mildred Hubble," Constance said. "But you may want to save your thanks until after we have solved the problem at hand. Here's the trapdoor."

They had, indeed, reached the top of the stairs at last. Whoever had built them had seemed not to think it necessary to include any sort of landing; the steps simply got smaller and more oddly shaped until they dead-ended at the square wooden trap like something drawn by a surrealist. The trap itself was secured with three heavy iron bolts, each the thickness of a thumb, which slid directly into the stone blocks that formed the stairwell's ceiling and the floor of the walkway above. Constance passed her lantern down to Mildred, and holding onto the topmost step so as not to lose her balance, shot the bolts back one at a time. Then she pointed her fingers and sent a controlled stream of magic at the door, raising it just enough so she could peer through the opening.

 _...in here_

 _...the..._

 _take it..._

 _...can't STOP_

whispered the voices, and this time Mildred heard the words in the babble too and called "Miss Hardbroom!" from below.

"Yes, Mildred, I know," Constance said over her shoulder. "Hold the lights. Don't let them go."

"Can you see anything?"

Constance pushed the door higher and craned her neck, and her heart gave a sickening lurch in her chest. There was nothing but more grey void above.


	4. Chapter 4

"Miss Hardbroom? What is it?"

Mildred's voice sounded very young and very frightened, but Constance had no reassurance to offer. Gripping the edge of the square opening, she pulled herself up another two steps, until her head and shoulders were outside, but still protected by the angle of the partially open trapdoor. The tower walkway had been one of her favourite places in the castle for years; she had come here often alone, late at night, to look out over wood and field and village and enjoy the quiet of a sleeping world. It upset her to see the view that she thought of as her own wiped away, replaced with this ugly blank expanse of something she did not understand.

"Miss Hardbroom!" Mildred clutched the hem of Constance's dressing gown, and galvanised into anger that was more than half fear, Constance ducked back through the opening to tell her off for it.

"Don't pull at me like that, girl, unless you want us both to fall to our deaths. It's a long way to the bottom of the stairs, in case you've forgotten."

"I'm sorry, Miss. I thought something had happened to you." Mildred's stricken expression said she was telling the truth, and Constance unbent a bit. Down there on her own, it was no wonder the girl's imagination was running away with her.

"Never mind, Mildred. Come and look for yourself. We shan't be able to see much, but we can get out of this hole, at least." She sent another shove of magic at the heavy trapdoor, and with a creak and a bang, it fell back flat, allowing her to climb out. "Pass the lanterns up first—we'll still need them—and then give me your hands." Mildred obeyed, and Constance clasped her wrists to steady her while she scrambled up the last few stairs, until they were kneeling face to face on the stones of the walkway.

"Oh _no_ ," Mildred said as she saw what Constance had seen. "It's everywhere—just _everywhere_."

"It certainly appears to be," Constance said grimly.

Mildred tipped her head back, and Constance watched her gaze in mingled terror and fascination at the grey barrier that arced over their heads. It skimmed just above the spire of the square east tower—the tallest of the three—and came down close along the castle's sides, blotting out everything as far as either of them could see. They might have been completely alone in the universe, marooned on an island that was the last vestige of anything real, if not for the voices that still swirled around them.

 _...this..._

 _...to help_

 _hush..._

 _...don't..._

"Is it safe to stand up, do you think?" Mildred asked timidly. "The stones are awfully hard on my knees. And wet."

Constance frowned at Mildred's grey school-issue nightgown, clearly sized for the much shorter first-year Mildred, and then at her own purple pyjamas, which were cold and sodden where she had crawled through a puddle on her way out of the trapdoor. It offended her sense of order and reason to think that an hour or two ago, a perfectly ordinary rain had been falling here, and now the sky from which it had fallen was gone. She felt a sharp prick of guilt, too, that this colossal event had happened entirely without her noticing. If she had been on guard, instead of lolling about in bed, might she have been able to stop it?

No, she thought. That way lay madness. She would just have to put it out of her mind for now.

"Yes, of course," she said to Mildred's questioning look. "It's high enough above us; we can't possibly stumble into it by accident as long as we keep clear of the parapet."

Mildred bounced up and busied herself collecting the lanterns while Constance got to her feet a bit more slowly. She would not choose to be fifteen again for any amount of money, but she could have used some of that youthful, elastic agility at the moment. The stair-climbing had taken more of a toll on her than she liked to admit, and she was fairly certain it wouldn't be the last challenge they faced before this was over, one way or the other.

"Here you are, Miss Hardbroom." Mildred handed her a lantern, and she took it with a gesture of thanks and held it up, scanning that maddening greyness for any sign of...well, anything. Unlike Mildred, she did not have much natural imagination and she knew it; even as a child she had preferred history books to fairy tales and struggled when asked to play games that began with "let's pretend." But all the same, she had a strong sensation that there were other eyes inside the greyness, or beyond it, that were looking back at her and her feeble pinpoint of light. It was not a pleasant thought.

"It seems as if you could rip it apart," Mildred said thoughtfully beside her. "If you could find a seam, or make a tear that was big enough. I mean, it is a _thing_ , isn't it? Something you can touch, not just nothingness."

Constance turned and looked at the girl, surprised. "Yes, well, Mildred, that would all be very well until you were pulled through your tear and disappeared forever." She paused. "But I understand what you mean. It does have that sort of feeling."

"Do you suppose that's what happened to everyone else?" Mildred asked. "Were they pulled into it somehow?"

"Well, perhaps we should consider that possibility," Constance returned. "Could they have been?"

Mildred bit her lip and fiddled with the chain on her lantern. "I don't see how. It's outside the castle and everyone was inside when they disappeared. Maud and Enid would have come to fetch me if they were going out—er, not that we would have gone out after bedtime, of course—"

"Oh no, of course not," said Constance with heavy irony. "Forget about that for the moment. Keep thinking it through."

"If it's only outside, then that means they couldn't have been caught in it unless it came into their rooms, and I don't think it did. It doesn't move about; it's fixed in one place."

"Thank goodness for that," Constance said. "What else? You've left a few things out of your analysis, haven't you?"

"Have I?" Mildred thought for a moment. "Well, I suppose whether it has anything to do with their disappearance or not, but it must, mustn't it? I mean, it's too weird to be a coincidence."

"You have a gift for understatement, Mildred. Go on. Think of the obvious questions."

"Is it a—a natural phenomenon, or something created by magic?"

"Yes, and?"

"And if it was created by magic, who created it, and why?" She looked at Constance for confirmation and got a nod. "And...there's something else, isn't there?"

"And," Constance said, "if everyone else is gone, why are you and I still here?"

... _here_ , whispered a voice in the chorus, as if echoing her.


	5. Chapter 5

Mildred's eyes widened at Constance's question. "I hadn't thought of that. Why _is_ it just us?"

"Why is it any of us, for that matter?" Constance said. "Two hours ago there were sixty-four people in this castle. If something had the power to make sixty-two of them disappear, I see no reason why it should have stopped there. Do you?"

"No," Mildred said slowly, her forehead furrowed with thought. "Unless..."

"What?"

"I'm not sure I ought to say it, Miss Hardbroom." Mildred looked down as if examining the toes of her fluffy pink slippers, now matted and muddy from the wet ground.

"This is hardly the moment to be coy, Mildred. Out with it, whatever it is."

"Well...what if one of us were the person who made the others disappear?" Mildred edged away from Constance a bit as she spoke, clearly trying to look as if she weren't doing it. "That person wouldn't make herself disappear too, would she? Or what if one of us isn't who she seems to be, like when Miss Cackle's sister pretended to be our Miss Cackle to get at us?"

"I am an only child and according to your school records, so are you," said Constance, "so that does for the wicked twin theory. But your suggestion is not without merit. One of us could, in fact, have made the others disappear." She folded her arms and regarded Mildred with a single raised eyebrow. "Do you think I could do such a thing, Mildred?"

"I'm sure you _could_ ," said Mildred in a faltering voice, "but...but I don't think you _would,_ would you?"

"No, I wouldn't," said Constance. "And if I had done, I assure you I would have seen to it that I got everyone in the castle, and we would not be having this conversation right now. As for you, if you had done it, it would have been an accident and you would have confessed as soon as you were caught. I think we can go on trusting each other."

"Oh, good," Mildred said, relieved. She gave Constance a cautious sidelong glance. "You're not cross that I thought it might have been you, are you, Miss Hardbroom?"

"Mildred, nothing gives me more pleasure than seeing one of my pupils apply logical thought to a problem, even if they slander my name in the process." Constance looked around the abandoned walkway and tower top. "I don't think we'll find anything else up here. We may as well go back inside where it's dry."

One at a time, they climbed back through the hole, and Constance replaced the door and fastened the bolts again.

"Do we have to go down the same way we came?" Mildred asked, looking toward the first turn in the staircase with a resigned expression.

"Not this time," said Constance. "Did you happen to pass through the kitchen earlier on your tour of the castle?"

Mildred nodded. "It was empty."

"All right then. Arms folded. Don't drop your lantern." As soon as Mildred had complied, she fixed their destination in her mind—a point just inside the kitchen door—and transported them both directly to it. Mildred stumbled as she materialised, and Constance, long accustomed to such things, reached out automatically to steady her.

"Thank you, Miss." Mildred uncrossed her arms and set both her lantern and Constance's in the centre of the work table. "It takes your breath away a bit, doesn't it?"

"Only the first hundred or so times," Constance said. "Sit down, Mildred. If we're going to continue this, we may as well do it over a hot drink."

"Really?" Mildred's eyes lit up with anticipation. "Can it be hot chocolate? Miss Cackle would—"

"I know she would," said Constance. In fact, it was because of Miss Cackle that she had conceived of this idea at all. She had been frustrated to the point of exploding in the past when the Headmistress insisted on stopping for tea and cakes in what seemed like times of the most urgent crisis, but she had to admit there was something calming about taking a few moments to collect oneself and think properly. A wave of desperate yearning for Miss Cackle's reassuring presence came over her, followed at once by dread that she might never hear that dry, precise, steady voice again, or worse, that she would hear it among the whispers that still surrounded them, even here.

"Yes, if you like," she said impatiently, seeing that Mildred was still waiting for permission, and Mildred went to find a pan in a cupboard and start heating milk.

"Mrs Tapioca taught us to make it with real chocolate chopped up," she said with her back to Constance, "instead of just powder. She said we were all too thin and needed more nourishment."

"Mm," said Constance, who had been told the same thing more than once by their former cook.

"I'm awfully worried about them, Miss Hardbroom." Mildred's voice trembled a bit, but she kept stirring the milk in the pan. "My friends, I mean. About everyone, really. I'd even be glad to see Ethel Hallow at the moment. Do you think we'll be able to get them back?"

"I hope so," Constance said.

Mildred turned around with a dismayed look on her face, spoon dripping milk onto the floor, and Constance looked back at her levelly. "Do you want me to lie to you, Mildred? You're not in your first year here; you've seen enough magic to know this is something completely out of the ordinary. Of course we shall do everything we can, but I have no more way of knowing whether we'll succeed than you do. And you're not the only one who's missing people, by the way."

She thought Mildred might cry, but the girl only squared her shoulders and went back to work, wiping up the spilt milk and then dropping chocolate bits into the pan to melt. Constance watched without really seeing, lost in her own thoughts, until Mildred set a slopping, overfull mug on the table in front of her and sat down in the chair opposite, hands curled round a mug of her own.

"So what do we do, then?" Mildred asked.

"Well," Constance said, "the original question still stands: why are we the only two left here? What have we in common that the others did not?"

"I'm not sure we have anything in common," Mildred said with somewhat tactless honesty. "Erm, we're both witches, but so was everyone else except Miss Drill. We're both female...tall...we both have dark hair..."

"That could describe dozens of the people who have gone," Constance said. She picked up her hot chocolate, and though she did not like sweet things much, took a sip to be polite. "It would follow that if we had been in the same place we might both have escaped, but we weren't; your room is two floors up and on the other side of the corridor to mine. What else?"

"I don't know."

"Don't give up now, girl. Think."

"I'm _thinking_ ," Mildred said, and Constance nearly dropped her mug.

"Say that again."

"I'm thinking?" Mildred said, baffled. "Why do you want me to say that?"

"You said the same thing when you first came to tell me what had happened," Constance said. "I remember. You were lying awake in the dark, thinking, and you heard the whispers begin a little at a time."

"Yes, but what—"

"You were awake thinking," Constance said. "I was awake reading. What if we were the only two people in the castle who were still awake? What if everyone else was taken in their sleep?"


	6. Chapter 6

The shadows in the corners of the kitchen seemed to grow deeper and colder after Constance's statement, and the whispers even more insistent. She and Mildred sat in their weak pool of candlelight and regarded each other across the table as the implications sank in.

"In their sleep?" Mildred said finally. "You mean, they were taken into a dream? Is that what we're hearing? The sound of their dreams?"

"Perhaps," Constance said. She lifted the mug to her lips again and watched Mildred over its rim as the girl thought about that. She had praised Mildred not long ago for using logic, but she knew that Mildred's real strength was in creative thinking and intuitive leaps, and she thought it was just possible that Mildred might see something she could not.

"Well..." Mildred said, "I suppose you _could_ put someone into a dream physically, if you wanted to. A dream is just something you imagine, after all, like a drawing. I can bring things from my drawings into the real world and send things from this world into that one, so I can see how it might work. Only, would it be all one dream, or a different dream for each person?"

"Which would you choose if it were you?"

"I thought you said you didn't think I had done it," Mildred said, going a bit pink.

"I don't," Constance said. "But you have a similar power to this one and I have not, so you are better equipped to guess at what our putative villain might have done." She allowed herself a thin smile. "I may never say this to you again, Mildred, but let your imagination run wild."

Mildred smiled back, seeming to appreciate the joke—a pleasing moment for Constance, whose humour was often taken the wrong way or went completely unnoticed—and then lapsed into silence while she considered the problem. As she thought, she twisted a long lock of wavy dark hair round her forefinger, and Constance drained the rest of her hot chocolate to avoid snapping at the girl to stop. She had been guilty of the same habit in her own youth, until her grandmother had disciplined it out of her, so she understood the impulse. What was more, she didn't want to interrupt whatever mysterious process passed for cogitation in Mildred's mind.

"I suppose," Mildred said after a minute or two, "if I wanted to make it easy on myself, I would have only one dream. It's hard to think of an idea for just one picture, and to imagine it and get all the details right, so doing dozens of them would be really difficult. But if I wanted to do it properly, I would have separate dreams for each person. If they were all in the same dream, they could get together and work out a way to escape, but on their own they'd be frightened and confused. They might not even know they were dreaming, or think they were still in their own beds and would wake up any time."

"Very sensible," Constance said. "It also means that neither you nor I dare fall asleep, or we may suffer the same fate without even realising it."

"How do we know we haven't already?" Mildred asked. "Perhaps in my dream, everyone is gone and we're the only two people left in the castle, and I think you're here talking to me, but really you're somewhere else having a dream of your own. Or this _is_ your dream, and you're dreaming about me dreaming about you talking to me. Or—"

Constance began to regret inviting Mildred to use her imagination. She felt the first warning throb of a tension headache and pressed her palms to her forehead, trying to quell it before it could get any further.

"This is not a dream, Mildred," she said firmly.

"But how do you know?"

"Because dreams are non-linear." She took her hands away from her head and drew a line on the table between herself and Mildred with one finger for emphasis, adding a little magic to make it glow. "Tell me about the last dream you had that you can remember."

"Erm..." Mildred screwed up her face, recalling it. "I dreamt I had gone to Spain, like I did over last summer holidays, but everyone spoke French instead of Spanish. I turned down a street and saw Enid selling ice creams from a trolley, and she said 'T'as l'air fatiguée, Millie,' and the ice-cream trolley turned into a bed, but it was also sort of a train, and then I was at home and I decided to have a bath, but the tap was broken—no, wait, actually that was before the Spain bit, and then—"

"All right, that's enough. Now tell me what has happened since you went to bed this evening."

"I heard the voices and I got up to find that everyone was gone, so I came to tell you. We saw the grey stuff outside and went up the secret stairs to the tower to see if it was everywhere, and it was, so we came here to talk it over—oh, okay, I see what you mean. If this were a dream, all of those things would have happened out of order, and we would have floated up the stairs holding onto bunches of helium balloons, because dreams don't make sense."

"Exactly," said Constance, privately hoping it was true. The thought of not knowing whether she was dreaming or not was horrifying to her at a deep, fundamental level, and she wished Mildred had not put it in her head.

"So we've got to stay awake."

"Yes," said Constance. "Which is going to become a problem very soon, I'm afraid."

"Really?" Mildred was interrupted halfway through the word by a yawn, as if just thinking about sleep were making her drowsy. "I mean, it is quite late now and I'm getting a bit tired, but I know there's a potion for staying awake. You use it, don't you? I saw it in your bag that time when I was a frog."

Constance sighed. "I do, Mildred, I do, but there are limits. Seventy-two hours is the very longest anyone should rely upon Wide-Awake potion. After that point, extremely undesirable side effects begin to set in."

"What sorts of side effects?"

"First confusion, then hallucinations. Very vivid, usually frightening ones."

"Oh," said Mildred.

"Yes," said Constance. "In the best case, I would be rendered helpless. In the worst case, I might injure myself or you while in the grip of a hallucination. It would be worse than if I had been taken into a dream." She glanced up at the clock on the kitchen wall, which helpfully informed her that it was just before one in the morning. "I am currently at the sixty-five-hour mark, which is why I was already in bed when you came looking for me—I meant to get a full night's sleep to reset the clock. Each dose lasts twelve hours, so if I take another one now, in seven hours I will pass the seventy-two-hour mark, and all bets will be off. On the other hand, if I do _not_ take another dose, at some time soon I simply will not be able to stay awake any longer, and then our dream abductor will do to me what he or she has done to everyone else."

"Take the potion," Mildred said promptly. "I don't want to be on my own, Miss Hardbroom. I'd rather have you here and off your head. Oh—that didn't come out right—but you know what I mean." She yawned again. "And I think I'll need some as well, please."

"Yes, well," Constance said. "There's one other problem: the potion has the potential to be addictive. I have managed my use over the years to stay ahead of it, but it takes a great deal of discipline and attention. As such, I am very reluctant to give you even one dose."

"But we really haven't any other choice, have we?"

"I suppose not," Constance said. She pushed their mugs aside and conjured the familiar corked bottle onto the table, then conjured two teaspoons from a kitchen drawer and poured out a careful dose for each of them. It had been ages since she had bothered to measure for herself, but the last thing she intended to do, after all she had said, was let Mildred see her drink directly out of the bottle. She swallowed her spoonful, and Mildred followed her example.

"Eurgh! It's bitter." The girl shuddered. "How can you bear it?"

"Like so many other things in life, Mildred, you get used to it," Constance said. "Do you feel a difference?"

Mildred nodded, scrubbing at her mouth with the back of one hand to remove any lingering traces of potion. "Yes, loads. It's more than just not being tired anymore, it's—it's as if everything is brighter and has sharper edges, and I can see farther and think more clearly." She raised her gaze to meet Constance's, and Constance saw one of the flashes of perceptiveness that had always unnerved her when dealing with Mildred. "I understand how people can get addicted. It's no wonder you've never taught us to brew it in lessons."

"You'll learn when the time is right," Constance said shortly. With a sharp jab of her fingers, she sent the potion bottle back to its place in her own room, and the mugs to the empty sink, where they rinsed themselves and turned upside-down on the draining board to dry. "And speaking of time, now that we've taken the potion, the clock is ticking. We have seven hours to sort this situation out."

"I hope that's enough," Mildred said.

"We shall just have to make certain it is," said Constance. "Arms folded."

Mildred obeyed, and Constance transported them both away.

 _Come..._

 _...if you..._

 _...stop_

 _...don't..._

 _...take it..._

 _What's that..._

 _...STOP._

whispered the voices in the deserted kitchen.


	7. Chapter 7

As the clock's hands crept from one to two, the castle's cats, unaffected by whatever had swept up their human mistresses, began emerging from the hiding places where they had taken cover when the voices began. On velvet paws, they slunk out from the shadows behind curtains and under tables, with ears cocked back and noses twitching delicately, gathering information from the air. They oozed through holes and lurked around corners, occasionally flattening themselves to the ground if a particularly strident voice startled them. The cats did not know exactly what had happened, but years of being steeped in witches' magic had made them cleverer than other cats, and they knew it was something suspicious. They convened in the deserted Great Hall, where they held a mostly silent conference and decided the best thing to do was wait and watch. In the meantime they would sharpen their claws, just in case. Cats liked to be prepared.

While the cats were attending to their own business, upstairs Mildred was dusty and out of breath, having just helped roll back the heavy, faded Persian carpet that covered the floor of Constance's room. The whispering was more muffled here than in other parts of the castle, perhaps because of Constance's layers of protective spells, but still quite audible if you paid attention: _come, stop, don't, help, here_.

"What are you going to do?" Mildred swiped the back of a hand across her forehead, leaving a grubby smudge on the pale skin, and regarded the bare flagstones with a quizzical expression.

"The scrying mirror was a failure," Constance said, "but it isn't the only magical artefact I own. Go sit over there, on the bed."

"Why?" Mildred eyed Constance's rumpled bed as if the covers might come to life and strangle her.

"Because I told you to, girl! Why do you always—" Constance stopped, drew a deep breath and tried to compose herself. "Because you're standing on the bit of floor I need to open, Mildred. Now will you kindly do me the favour of moving out of the way?"

Rather hesitantly, Mildred went and sat at the bed's lower right corner, one arm looped round a bedpost and her slippered feet drawn up for safety. Constance knelt, murmured a word and pressed her right hand flat on a stone that some medieval builder had cut and shaped centuries ago, and with a faint scraping noise, it tilted and slid back under the stone beside it, leaving a dark hole in the floor.

"That would make a good place to keep your food for secret midnight feasts," observed Mildred from the bed, "if this were one of those school stories."

"Yes, well, it isn't," said Constance, whose only memories of midnight feasts at school were of not being invited to them. She leant down into the hole, all the way to her shoulders—the space, in fact, was large enough for two or three witches to hide in, and had often been used for exactly that purpose in the past—and pulled out a glass lamp with a heavily charred wick.

"Oh, a spirit lamp," Mildred said. "But we have lots of those in the potions lab."

"Not like this one," said Constance. "When you light it, the flame reveals things that are invisible." She set the lamp to one side and reached into the hole again, drawing out a round, chased silver case that just fit into the cup of her palm. "This is a magical compass; it shows you in which direction a spell was cast. And this is an unbreakable rope."

"It's awfully thin," said Mildred, regarding the coiled loop of glittering filament.

"Don't be so certain," Constance said. "The only blade that can cut it is this one." She undid the drawstring at the top of a black cloth bag and shook out a clasp knife with writhing, interlocking symbols incised along its handle. "I spent three years' worth of holidays hunting through marketplaces and magic shops for the blade after I found the rope. I'm told they were made as a pair, but separated later. Anyway, they're together again now."

Mildred was looking at her with an odd expression, as if she had never considered that Constance might have a hobby, or indeed leave the castle between school terms. She chewed distractedly at a shred of fingernail while Constance pulled a few more odds and ends from the storage space and then slid the covering stone back into place with a gesture, locking it with another murmured word.

"Does Miss Cackle know you have all of this?" Mildred asked around the finger in her mouth.

"Of course she does," Constance said crossly. "And don't bite your nails. How many times have I told you girls it's unhygienic?"

"Sorry, Miss Hardbroom." Mildred removed her finger, looking contrite. "I just wouldn't have expected it, that's all. You don't like it when we enchant things."

"When you and your friends enchant things, Mildred, you make robot dogs that try to take over the world and pinball machines that summon wicked witches out of the past. These are classic enchanted objects, elegant and useful, with a history to each one. There is a difference." Constance planted her hands on her hips and was reminded that she was delivering this lecture while dressed in damp, dirty pyjamas. She felt it detracted from her authority somewhat, but there wasn't exactly time to stop and change. There were only a few hours left before the side effects of the Wide-Awake Potion set in-she already had the quivery, unsettled sensation that was the prelude to the downward spiral-and she wanted to be safely in her bed with Miss Cackle to watch over her before that happened.

 _Oh, Amelia, please come back_ , she thought in a moment of temporary despair, and had to blink away tears.

"Miss Hardbroom? Is everything all right?"

Constance cleared her throat. "Quite all right, Mildred. And we're wasting time. Where is your schoolbag right now?"

"In my cupboard," Mildred said.

"Well, fetch it here then."

Mildred went through the words of the summoning spell and the bag appeared at her feet—not a bad effort at all, the teacher in Constance noted. The bag was bulging, and with an apologetic look, Mildred upended it on the floor, releasing an avalanche of crumpled half-finished sketches, chewed pencil stubs, sweet wrappers, exercise books with bent covers, bits of cheap (and forbidden) jewellery, a tube of hand cream and a lone trainer with its laces knotted together. Constance rolled her eyes, but took the empty bag from Mildred and loaded the enchanted artefacts into it, leaving aside the compass.

"I'm going to trust you to carry the bag, Mildred, and you're going to be very careful with it, aren't you?"

"Yes, Miss Hardbroom."

"Good," Constance said. She found her slippers under the edge of the bed and put them on—she had no desire to traipse about the corridors in her bare feet any longer—then put on her Chinese silk dressing gown for good measure, tying it firmly in place. Thus arrayed, she flipped open the silver case and looked at the compass, which emitted a faint purple glow from its face.

"All right, Mildred. If this is a dream-spell, then we are going to find out where it came from."

"Then what?"

"Then," said Constance, "we shall see."


	8. Chapter 8

As they returned to the corridor, Mildred pulled the door closed, cutting off the warm, well-lit haven of Constance's room and leaving them in the eerie glow of the compass face.

"Should I light the lantern again?"

"Not yet. S _cientia potestas est_." Constance passed her free hand over the compass and watched the needle quiver, then swing round to point down the left side of the corridor. At the same time, the compass itself twitched, tugging her in the correct direction.

"This way," she said to Mildred. "Stay near me."

Mildred, not needing to be told twice, edged right up against Constance until their arms touched. It was closer than either of them would have wanted to be under ordinary circumstances, but these were far from ordinary circumstances.

Together, they took a step forward.

... _HERE_ , hissed one of the disembodied voices, making Constance start. It sounded as if the voice's owner were standing directly in front of them, but all she could see was the corridor stretching away into the dark like a tunnel with no end. Somewhere in the distance, there was a small, echoing _clink_ , as if something metallic had fallen over, and she felt a chill like a corpse's finger drawn softly down the middle of her back.

"Is something the matter?"

"What?" Constance looked at Mildred, confused, and saw worry written all over the girl's face.

"You've stopped," Mildred pointed out.

"I..." Constance cleared her throat, which suddenly felt dry and sticky at the same time, as if she'd swallowed a mouthful of cobwebs. "I thought the compass might be recalibrating." She tapped the glass face with a neatly filed fingernail. "It isn't, though. Come along."

Mildred still looked uncertain, but her conditioning to submit to orders given by teachers was stronger than any doubt she might have had, at least for the moment, and she followed Constance's lead as they made their way along the corridor, guided by the compass's needle. It led them past a bathroom and then the row of first years' rooms, all with their doors standing open to reveal narrow, empty beds inside. The scratchy grey blankets were rumpled, but not thrown back, and Constance got a horrible image of the sleeping girls vanishing from beneath them, one by one, leaving nothing behind but the outlines of their bodies and the impressions of their heads on the pillows.

"Were the doors open when you came down?"

Mildred shook her head, dark hair swirling loose around her shoulders. "I opened them. I was feeling pretty desperate to find anyone at all by the time I got to this floor." She bit her lip, and even in the low light, Constance could see her eyes fill with tears. "I hope the first years are all right. I mean, I hope everyone is, of course, but they're only kids."

"I know," Constance said. "But the only way we can help them is to keep going. Straight ahead, and then the stairs to the ground floor are next." She took a firmer grip on the compass, not wanting Mildred to realise how badly her hands were beginning to tremble, or that she was feeling more unwell by the moment. This was all happening faster than she had expected, and it terrified her-or was that the potion at work? It had been years since she had pushed herself this close to the edge, and she'd been younger and stronger then. Who knew how the strain on her body might affect her now?

As they reached the head of the stairs, from the corner of her eye she saw a flicker of movement-something dark and misshapen and low to the ground, scuttling along the base of the corridor wall-and gasped aloud before she could stop herself.

"What is it?" Mildred spun around to look.

"Nothing." Constance heard a quiver in her voice and cursed herself. "Really, nothing. One of the cats perhaps."

"I haven't seen any of the cats in hours either," Mildred said warily.

"Just because you haven't seen them doesn't mean they aren't there, you idiot girl! I said it was nothing and I meant it, so keep walking. We both know you're an incompetent fool, but even you can't stuff that up, can you?"

 _You.._. _you..._ came a whisper.

Mildred seemed to hear the voice as well this time, but instead of obeying, the girl dug her heels in, stopped and faced Constance over the open compass. Its light illuminated her features horribly from below, and all at once Constance saw a grinning skull where her face ought to be. The sight made her stomach lurch, and she wondered if she was going to be sick in front of Mildred. She hoped not, but anything was possible.

"You said hallucinations were one of the side effects of too much potion. Is it happening already?" Skull-Mildred sounded scared but determined. "Tell me the truth, Miss Hardbroom. I need to know."

Constance swallowed hard and narrowed her eyes, and Mildred's face wavered and reshaped itself into its proper, familiar form. "It might be. Only a bit, though. It doesn't happen all at once."

"Are you sure?"

"Yes."

"That it's only happening a bit, or that it won't happen all at once?"

"Both," Constance said. She hesitated and then admitted the rest of it. "But it's happening more quickly than I expected. I don't know why, but I do know we need to hurry, so please, Mildred, we have to keep walking. Hold out your hand."

Mildred did as she was told, and Constance pressed the magic compass into it, curling the girl's fingers around the case. "You had best hold onto this until I feel steadier. Just follow the needle, or go where you feel the pull. It will be stronger as we get closer to the source of the spell, so hold it tight, or it may pull itself right out of your hand and be damaged. Do you understand?"

Mildred nodded.

"Good," Constance said. "And Mildred...I didn't mean what I said a moment ago. You are not a fool or incompetent, whatever I may have told you in the past. In fact, if you must know, I am actually quite proud of everything you've learnt since you came here. Try to remember that if I start raving again, will you?"

"I'll remember," Mildred said with a faint smile. "All right, if we've got to keep walking, let's walk. Do you want to hold my hand or anything?"

"I should hope I'm not _that_ far gone yet," Constance said. "Down the stairs, Mildred, at the double."


	9. Chapter 9

They went down the steps and into the vaulted entrance hall, with Constance carrying the lantern and Mildred holding the compass case in both hands to keep it under control. It was pulling hard toward the double doors that led to the Great Hall, and Mildred's jaw was set and rigid with the effort of holding it. As they approached, Constance flicked a hand at the doors, which swung open, revealing blackness inside, and letting the hall's familiar musty, dusty smell of old wood and cloth come rushing out. It should have been comforting, but instead just reminded Constance of how wrong everything was. Would she ever see the entire school gathered in this room again, or stand on the dais at Amelia's side in her role as deputy? Just at the moment, she would have given anything for a long, dull assembly with Miss Crotchet banging out tunes on the organ behind her.

"It wants to go in there," Mildred said tensely, inclining her head toward the compass, which quivered with eagerness at the end of her outstretched arms like a pointer that had sighted a rabbit.

"Well, that's where we shall have to go, then."

"Have I got to go first?"

"You are the one with the compass, Mildred."

Mildred drew a deep breath. "All right."

The girl took a hesitant step through the doorway, then another, and then she screamed—not the overwrought teenage shrieking that Constance heard so much of around the school and that always set her teeth on edge, but a real, full-throated cry of surprise and fear. Before Constance could react to it, she saw what Mildred had seen and stopped cold just inside the threshold.

The Great Hall was full of sinister ghost lights, dozens upon dozens of them, shining eerie and greenish-yellow from every surface high and low, and at ground level seething about and drawing relentlessly closer to where the two witches stood. Constance imagined them swarming over her and consuming her, tearing the flesh from her bones, and as she recoiled, her hands came up to cast the most powerful spell she could think of, something that would burn everything in its path to ashes. The lantern fell at her feet and smashed, spraying glass and hot wax across her slippers and her bare ankles above them, and the candle inside rolled away, flame guttering madly before going out.

"No, don't do that!" Mildred let go of the compass with one hand, flung her arms round Constance to hold her back, and caught hold of the compass again on the other side of Constance's body before it could get away.

"Let me go, Mildred!" Constance fought against the restraint, but Mildred held her fast with astonishing, panic-fuelled strength. "Let me go, are you mad, I have to fight them—"

"It's all right, Miss Hardbroom. It really is the cats this time. Please stop or I'll lose hold of the compass."

Constance stopped struggling. "What are you saying?"

"It's the cats," Mildred said again, and Constance could feel her shaking with relief. "It's their eyes reflecting the light. They do look awful though, if you're not expecting them."

"Are you sure?"

"I'm sure." Mildred let Constance go and stuffed the compass down into the bag for temporary safekeeping, buckling the flap to stop it escaping. Constance heard her fumbling for something on the floor, and then she relit the extinguished candle and wedged it into one of the iron brackets on the wall. "I think it's all of them. They're all here in the hall, that's why we haven't seen them round the castle. Look, here's Tabby, and this one's your Morgana, isn't she?"

The girl bent down again and popped back up with a furry black shape, which she bundled into Constance's arms. Morgana's small body was electric with tension, her tail lashing, but she rubbed her head against Constance's chin and gave a soft, querying chirp, as if to ask whether Constance knew what was going on.

"I need to sit down," Constance said faintly. Still holding the cat, she found the nearest chair and sank into it, and Morgana swarmed up onto her shoulder and hooked claws through the layers of her dressing gown and pyjamas to balance there. She felt a vague, faraway pain and looked down to see thin blood trickling from a scratch where the lantern glass had cut her. Well, she supposed it could have been worse.

"Are you hurt?" she asked Mildred.

"I'm all right." Mildred had gathered Tabby up and was nuzzling the top of his head. "You gave us an awful fright, Tabs. What are all the cats doing down here? Did you see what happened to everyone?"

In her disoriented state, Constance half expected Tabby to answer—she wouldn't have put it past Mildred to have a talking pet, just to make herself interesting—but the big grey-brown cat only let out a low, rumbling noise that was somewhere between purr and growl. Mildred kissed him on the ear and put him down again, warning him to mind the broken glass, and he picked his way to a chair, leapt up onto it, and sat down, tail curled round his paws.

 _Well? Get on with it_ , his body language seemed to say.

"Do we keep following the compass? I can still feel it pulling." Mildred indicated her schoolbag, which was standing away from her body on its strap with the energy of the compass inside it.

"Yes. Down, Morgana." Constance detached Morgana and set her on Tabby's chair, where she was surprised to see her turn and give the other cat a friendly lick on the shoulder; she hadn't known Morgana and Tabby were acquainted. There were cats everywhere, perched on the seats and curled on the dais and stretched out along the windowsills, where the beautiful stained-glass panes were blank and dull with the mysterious grey substance outside them. The cats blurred in front of her, seemed to double and triple in their numbers, and she blinked hard, trying to force them back into reality.

"Now," she said to Mildred, who was watching her with wary eyes, as if she thought Constance might need restraining again. Obediently, Mildred fetched the compass out of the bag and grimaced as it pulled her arms out straight with a bone-jarring jerk.

"It's getting hot to touch," she said. "Is that meant to happen?"

"It means we're closer to the source of the spell," Constance said. She stepped up onto the dais, rummaged on the shelf behind Amelia's lectern there, and brought out a tall beeswax ceremonial candle, which she lit, leaving the other candle in its bracket. If things went wrong, at least they would have a light near the door to escape by "Forward, Mildred."

Mildred walked forward and Constance followed her, candle held aloft, as the cats' glowing eyes watched their progress. The voices were growing louder and more excited, speeding up into a near-gabble in which the words ran together.

 _...comehere..._

 _Ifyou..._

 _HelphelphelpHELP..._

"It's awfully hot now, Miss Hardbroom," Mildred said through gritted teeth. "It's starting to burn a bit actually. Could you cast a cooling spell on my hands or something?"

"Not without confusing the compass. Here." Constance let go of the candle, which remained floating gently in the air beside her, pulled the green silk sleeves of her dressing gown down over her hands to form makeshift mittens, and then took the compass from Mildred. "Now put your hands over mine, so I won't lose my grip if I—if I see something that isn't there."

Mildred obeyed, and together they crossed the remaining empty space that ran along the front of the dais, moving toward the windows at the far side of the Great Hall. As they went, the cats cleared a path for them like the Red Sea parting. The compass drew them right up to the wall, where it pulled their joined hands against the carved wood panelling with a muffled thud and then stopped, quivering in what appeared to be frustration.

"But there's nothing here," Mildred said, confused. "I thought it would lead us to a person, or at least a charm scroll or something like that. How can this be the source of the spell?"

As if in answer to her question, the compass made a huge, sudden leap that neither of them were expecting. It wriggled away like a fish, shot toward the ceiling, then made a sharp turn, punched through the window just above their heads, and vanished into the void of nothingness outside.

"It can," Constance said, staring at the neat, round hole in the window's leaded glass, "if the source of the spell is outside the castle wall, on the other side of the barrier. Would you care to make a guess as to what that means, Mildred?"

"We have to go into it," Mildred said grimly.


	10. Chapter 10

"Yes," Constance said. "That is exactly what we shall have to do."

"But if we go into it, won't we just be lost like the compass was, and the book and the pencil?" Mildred looked pale and troubled at this prospect. "We still don't know what's on the other side, and you—well—you're not quite yourself at the moment, Miss Hardbroom."

"I'm not quite all the way round the twist yet, Mildred," Constance said dryly. "And I think you're forgetting that we have other tools at our disposal besides the compass. Open the bag."

Mildred obeyed, and Constance reached in and pulled out the thin coil of unbreakable rope. Its silver and gold threads caught the light of their floating candle and glinted, giving it an otherworldly, fairytale look that appeared to change Mildred's earlier opinion of its usefulness.

"You mean, we'll attach the rope to something in here, and then attach ourselves to the rope and jump through?"

"Not precisely," Constance said. "If you go flying through the barrier at top speed and then suddenly come to a stop when the rope runs out, you're likely to be cut in half, or have a limb pulled off like a fly's wing. And as you've just reminded me, we don't know anything about what's on the other side. It could be a raging inferno. Or a brick wall." She unbound the rope from itself and shook it out across the floor, where one of the cats promptly pounced on its trailing end and rolled over, biting and kicking at it.

"No, Midnight," Mildred said reprovingly. "Behave, or I'll tell Maud when I see her." She removed Midnight from the rope and sat her on Miss Cackle's lectern, out of temptation's way. "So how can we use it, then?"

"Do you remember what you said about the grey cloud earlier, when we were on top of the tower?"

Mildred crinkled up her brow, thinking. "That it seemed like something you could pull apart."

"Yes," Constance said. Still holding the rope in one hand, she considered the rows of chairs, the lectern and the table and dismissed them all as too flimsy, then spotted a stone support pillar nearby and wrapped the rope around that instead. "And I agreed with your assessment, so I thought we would test the theory. If we can create a large enough opening, perhaps it will equalise the pressure on both sides and we can go across at a normal speed, instead of being popped through like a pair of corks."

"So the rope..."

"Will hopefully keep us from being pulled in until we can make that opening." Constance tied a hard knot in the loop she'd made round the pillar, mentally cursing her trembling hands, and fused it with magic to be certain it would hold. She hadn't suffered an hallucination since the cats' eyes, but she felt lightheaded and detached, as if she were standing just slightly to the left of her own body and watching herself tie the rope and speak to Mildred. Somewhere in the heavy blackness of the entrance hall, she heard the big grandfather clock strike three, helpfully reminding her that she now had only five hours left—or less, considering the speed at which things were progressing—before her descent into potion-induced madness was complete. She felt a muscle twitching involuntarily in her cheek and hoped Mildred couldn't see it.

She returned to the broken window, paying out a long length of rope behind her, and wrapped the loose end twice round Mildred's waist, then twice again round her own, and knotted it.

"Shouldn't it be tighter than that?" Mildred's voice was nervous and quivering, as if she might break down in tears, and Constance felt a moment of sympathy for her, but concealed it. Pity was a luxury neither of them could afford at the moment.

"We need enough slack to reach the window and through it to the barrier," she said. "Perhaps you'd like to do the levitation spell? If you know the words, that is."

"We only learnt them in first year." Now Mildred sounded scornful, distracted from her fear by pride just as Constance had intended her to be. " _Altus, alta, alto, altissima_!"

Gently, they both rose from the floor and up the short distance to the windowsill, which was just wide enough for them to kneel on side by side, holding on with a hand each to the wall. Through the hole the enchanted compass had made in its escape, Constance could see the grey substance that surrounded them, maintaining the same arm's-length distance from the castle proper as it had outside her bedroom.

"All right, Mildred. Don't move or touch anything until I say." Constance raised her hand and with a sharp gesture, banished the glass, leaving nothing but empty air between them and the greyness. She leant out past the window's frame, stretching toward the barrier, but before she could touch it, she was overwhelmed by a sudden sick certainty that she was balanced on the edge of a precipice with a yawning chasm underneath her. When she looked down it was there, vast depths spinning dizzily away to a vanishing point that seemed miles below, and she felt herself tipping forward and scrabbled for purchase, fingers scraping over the rough stone of the sill. She opened her mouth to scream, to cry out an incantation that would save her, and then someone grabbed her hard and jerked her backward.

"Miss Hardbroom!"

Constance stopped, breathing hard, hair hanging in her face. "Mildred?"

"It's happening again." Mildred's fingers dug into her shoulder like steel pincers. "You're seeing something that's not there."

"I thought..." Constance swallowed. "I thought I was falling." The weak, whingeing sound of her own voice disgusted her, and she closed her eyes for a moment in embarrassment.

"You can't," Mildred said. "The rope, remember? And we're not far enough from the ground for you to be really hurt anyway, even if you did fall. Look."

"Never mind, Mildred. I believe you." She straightened up and tried to regain some semblance of dignity. "Perhaps it's all right for us to try at the same time, if you're not frightened."

"I'm scared silly," Mildred said simply. "But I'll do it anyway, if you need me to. On three?"

"Very well."

"One," Mildred said.

They both leant forward, reaching for the barrier again.

"Two."

Constance raised her hand, fingers hooked into claws, and poised it just above the grey substance.

"Three."


	11. Chapter 11

Constance had imagined the grey substance would be thin and taut to the touch, but it was softer than that, putting up an almost fleshy resistance that made her stomach turn. She could feel it coating her fingers and collecting under her nails, as if she were trying to scrape apart a wall of heavy clay or mud. Beside her, Mildred was making small, disgusted noises, but kept doggedly tearing at the surface all the same, peeling away layers and layers of grey stuff with no result. After a few moments, she stopped, shaking her hands briskly in an attempt to clean some of the muck from them.

"I don't think we're getting anywhere, Miss," she said. "When you try to tear it apart this way, it just goes on forever. We need to come at it straight on, the way we did with the pencil and things." She jabbed her forefinger at the barrier, and it made a dent, sank in, and then breached the surface with the same soft pop Constance remembered from earlier in the evening.

"Oh!" Mildred's eyes went wide.

"What is it?"

"It's _pulling_ ," Mildred said in a strained voice. "It feels as if it's trying to suck my whole arm in."

"That's the vacuum." Constance hurriedly checked the knots she'd tied in the magical rope to be certain they were secure. "We've got to make the hole larger now you've broken through." She stretched farther over the windowsill and sank two of her own fingers in just above Mildred's, until she felt the suction catch hold of them and tug. It was impossible to tell what the atmosphere on the other side was like, except that it was chilly rather than hot. At least they weren't about to be burnt to a crisp by a roaring wall of flames, she thought.

"Help me pull it wider," she said to Mildred. "Like this, in opposite directions. And brace yourself."

With her combined strength and Mildred's, they wrested open a hole the size of a tennis ball, and as they did, the ever-present whispers surged, becoming louder and clearer at the same time, knitting the snatches of words and phrases together into complete sentences.

 _If you…_

 _...come_

 _...here..._

 _Where?_

 _In here. It's opening._

 _Do you think it's someone coming to help?_

 _I don't know yet. Go and get her._

 _I can't…_ a voice began, but was cut off as Mildred lost her grip on the edges of the hole they'd made and it snapped shut again, turning the rest of whatever the voice had been going to say into a muffled murmur.

"Oh no," Mildred groaned. "I'm sorry—I'm sorry—it just slipped!"

"It's all right, Mildred." Constance leant her forehead against the stone surround of the window, trying to catch her breath. "We'll rest a moment and then give it another go. It may be easier now we know what to do."

"Okay." Mildred flexed her fingers as if they ached. "Did you recognise that voice? The one that said 'it's opening?'"

Constance nodded. "It was Miss Drill."

"That's what I thought," Mildred said. "And the voice answering her sounded like Ethel. Do you think they're really there on the other side?"

"I hope so," Constance said. A wash of giddiness swept over her, and she deliberately fixed her eyes on the grey barrier in an attempt to avoid hallucinating that bottomless chasm again, or something even worse. She could feel magic fizzing and sparking and itching in her fingertips, her body's automatic response to what it thought was an imminent threat. They needed to get to a safe place before it built up to the point where it began spilling out on its own; she hadn't experienced a Tesla discharge like that in a long time, but she hadn't been this agitated and off balance in a long time, either.

"Very well, Mildred," she said. "We'll try again now, and you mustn't let the voices distract you. Whatever happens, keep pulling as if someone's life depends on it, because it may."

"Yes, Miss Hardbroom." Mildred's frightened face reshaped itself into firm, adult lines, and for the first time, Constance saw a pure, crystalline glimpse of the witch that Mildred would be in just a few more years, sure of herself and confident in her powers. She'd seen many girls make that transition over the years, but had never expected Mildred Hubble to be one of them. Perhaps, she thought, she might yet be proven wrong. If so, she might even be glad to admit it.

"Now," she said to Mildred, and as one, they pierced the barrier again and wrenched it in opposing directions, expanding the gap past its previous size to the diameter of a dinner plate, then a cauldron's rim. Constance could see nothing clearly through the opening, only vague shapes, some hard and vertical, some just coloured blurs; it made her uneasy, but she kept pulling anyway, knowing she couldn't trust her own perceptions at the moment.

 _Come quick_ , said Miss Drill's voice on the other side, _I think_ _it's almost_ —

 _Constance!_ said another voice, and Constance knew this one too, knew it so well and had yearned to hear it for so long that the sound brought hot, stinging tears to her eyes. The hole in the barrier was wide and ragged now, with its edges fluttering limply as the last of the pressure equalised. She pushed Mildred through first and flung herself after, landing hard on an unyielding surface with a painful jolt. Her teeth came together in a sharp snap that left her tasting her own blood.

"But it's the castle," Mildred was saying, somewhere to her left. "We _left_ the castle. How can we be back in it?"

"What?" Constance forced her eyes open and sat up, only to discover that Mildred was right; they were back in the Great Hall, but a Great Hall empty of its seething masses of cats, lit by a brilliant light that streamed in through the stained-glass windows and cast dancing kaleidoscope patterns on the floor.

"Constance!" that familiar voice said again, so close now that it could only be in the same room with them. Constance turned, still dazed, to greet the Headmistress, but instead of Amelia's untidy grey hair and bright blue eyes and impish smile, she saw a monstrous thing: a misshapen creature looming three times the height of a witch, with glistening skin the colour of a bruise and writhing tentacles where its limbs should have been; a Great Old One from a story; an abomination.

"Constance," the creature said in Amelia's voice, and its tentacles squirmed eagerly. "Oh, Constance, at last. I am so glad to see you."


End file.
